+/*
+ * Taken from table 8-55 in the MPC8641 User's Manual and/or 9-61 in the
+ * MPC8572 User's Manual. Each line represents a syndrome bit column as a
+ * 64-bit value, but split into an upper and lower 32-bit chunk. The labels
+ * below correspond to Freescale's manuals.
+ */
+static unsigned int ecc_table[16] = {
+ /* MSB LSB */
+ /* [0:31] [32:63] */
+ 0xf00fe11e, 0xc33c0ff7, /* Syndrome bit 7 */
+ 0x00ff00ff, 0x00fff0ff,
+ 0x0f0f0f0f, 0x0f0fff00,
+ 0x11113333, 0x7777000f,
+ 0x22224444, 0x8888222f,
+ 0x44448888, 0xffff4441,
+ 0x8888ffff, 0x11118882,
+ 0xffff1111, 0x22221114, /* Syndrome bit 0 */
+};
+
+/*
+ * Calculate the correct ECC value for a 64-bit value specified by high:low
+ */
+static u8 calculate_ecc(u32 high, u32 low)
+{
+ u32 mask_low;
+ u32 mask_high;
+ int bit_cnt;
+ u8 ecc = 0;
+ int i;
+ int j;
+
+ for (i = 0; i < 8; i++) {
+ mask_high = ecc_table[i * 2];
+ mask_low = ecc_table[i * 2 + 1];
+ bit_cnt = 0;
+
+ for (j = 0; j < 32; j++) {
+ if ((mask_high >> j) & 1)
+ bit_cnt ^= (high >> j) & 1;
+ if ((mask_low >> j) & 1)
+ bit_cnt ^= (low >> j) & 1;
+ }
+
+ ecc |= bit_cnt << i;
+ }
+
+ return ecc;
+}
+
+/*
+ * Create the syndrome code which is generated if the data line specified by
+ * 'bit' failed. Eg generate an 8-bit codes seen in Table 8-55 in the MPC8641
+ * User's Manual and 9-61 in the MPC8572 User's Manual.
+ */
+static u8 syndrome_from_bit(unsigned int bit) {
+ int i;
+ u8 syndrome = 0;
+
+ /*
+ * Cycle through the upper or lower 32-bit portion of each value in
+ * ecc_table depending on if 'bit' is in the upper or lower half of
+ * 64-bit data.
+ */
+ for (i = bit < 32; i < 16; i += 2)
+ syndrome |= ((ecc_table[i] >> (bit % 32)) & 1) << (i / 2);
+
+ return syndrome;
+}
+
+/*
+ * Decode data and ecc syndrome to determine what went wrong
+ * Note: This can only decode single-bit errors
+ */
+static void sbe_ecc_decode(u32 cap_high, u32 cap_low, u32 cap_ecc,
+ int *bad_data_bit, int *bad_ecc_bit)
+{
+ int i;
+ u8 syndrome;
+
+ *bad_data_bit = -1;
+ *bad_ecc_bit = -1;
+
+ /*
+ * Calculate the ECC of the captured data and XOR it with the captured
+ * ECC to find an ECC syndrome value we can search for
+ */
+ syndrome = calculate_ecc(cap_high, cap_low) ^ cap_ecc;
+
+ /* Check if a data line is stuck... */
+ for (i = 0; i < 64; i++) {
+ if (syndrome == syndrome_from_bit(i)) {
+ *bad_data_bit = i;
+ return;
+ }
+ }
+
+ /* If data is correct, check ECC bits for errors... */
+ for (i = 0; i < 8; i++) {
+ if ((syndrome >> i) & 0x1) {
+ *bad_ecc_bit = i;
+ return;
+ }
+ }
+}
+